The invention relates to an adaptive testing method of generating a partial report such as for iconic memory. The invention also relates to an apparatus, such as an electronic device or computer system, for implementing the adaptive partial report procedure.
It has been known that human memory is composed of three sub-storages: sensory memory, short-term memory, and long-term memory. Sensory memory is the literal, modality-specific neural representation of sensory stimuli in the human brain. Sensory inputs from the environment are initially stored in sensory memory and processed in subsequent stages of perception and cognition. The existence of sensory memory was first demonstrated in the 1960s, in experiments in which three rows of letters were briefly displayed, and observers were asked to report the identity of the letters in one of the rows cued with a high, middle, or low frequency tone after a variable delay.
For example, FIG. 1a is an illustration of screen shots for a partial-report procedure. After a brief presentation of stimulus (a 3×4 array of letters) followed by a blank screen, the observer is given a sound cue. The observer is to report letters of the cued row in the partial report condition. Item recognition in the partial-report condition was compared with the whole-report condition, in which observers were asked to report all items from the display. FIG. 1b provides exemplary results of a partial report experiment. The performance difference between the partial report and whole report conditions is called the ‘partial report superiority effect’. The effect demonstrates performance benefits from iconic memory. The number of the estimated available items in sensory memory decreases rapidly with increasing test delay in partial report and approaches the whole-report asymptote in about 200-300 ms.
During the past half-century, sensory memory has been extensively studied and has been widely accepted as a critical component in many theories on human information processing. Recently, one of the inventors of this application compared, as part of a study, iconic memory decay functions of young, old normal, and old observers with mild cognitive impairment (MCI). The study found that iconic memory decayed much faster in the MCI group than the others (FIG. 2). FIG. 2 is a graph representing a decay function of three groups of observers or subjects. Because more than 80% of people with MCI develop Alzheimer's disease in 10 years, this finding suggested that faster decay of iconic memory might be an early sign of Alzheimer's disease.
Conventionally, the method of constant stimuli (MCS) is used to measure the memory decay function. Subjects' (or observers') responses at a number of pre-selected cue delays are measured with about 100 trials per delay. An empirical memory decay function is obtained by estimating the number of available items in sensory memory at each delay from observers' responses. Often a theoretical curve such as an exponential decay function is fit to the empirical data to characterize the memory decay process. In a typical study, between 600 and 800 test trials (6-8 cue delays×100 trials/delay) are necessary to obtain a good estimate of the sensory memory decay function. It takes approximately one hour for normal young observers but much longer for observers in special populations. The long testing time makes it difficult or even impossible to carry out partial report experiments in special populations.
Many adaptive procedures have been developed to reduce the burden of data collection in psychophysical experiments. Most development has focused on characterizing psychometric functions, including various non-parametric procedures for estimating a single threshold, and Bayesian adaptive procedures for estimating either a single threshold or the threshold and slope of a psychometric function. Recent development in this area has extended adaptive procedures to measure various psychological functions, including the threshold versus contrast function, contrast sensitivity function, and sensitivity and bias parameters in Yes-No tasks. In all these adaptive procedures, the stimulus in the next trial is determined by the observer's previous responses to improve the efficiency of the test.